The Martinos Center for Biomedical Imaging is a leading imaging resource located at the Massachusetts General Hospital. The mission of the Center is to develop and apply innovative biomedical imaging technologies to improve understanding of the pathophysiology and treatment of disease, and as a window to the function of the mind and brain. The Center provides state-of-the-art imaging technologies including MRI, MEG, PET, optical imaging, and advanced image-processing capabilities to hundreds of investigators worldwide. While the Center currently operates two 3 Tesla MRI systems (Siemens MAGNETOM Allegra and Trio), the recent explosion in the use of high field MRI for functional brain mapping has led to a demand for these resources that exceeds our present ability to accommodate. Our 3T systems are now shared by more than seventy investigators whose productivity is greatly diminished by the insufficient availability of imaging time. The goal of this proposal is to obtain partial funding for a Siemens MAGNETOM 'TIM' Trio 3 Tesla MR system for the Martinos Center resource. The proposed system will alleviate overcrowding on the present systems allowing currently funded investigators sufficient imaging time to accomplish their research goals. Features of the Trio that make it our system of choice include a large patient bore, a wide range of RF coils (including multi-channel array coils) that provide outstanding sensitivity, its speed of image encoding which greatly reduces image susceptibility artifact, excellent gradient linearity enabling a range of imaging protocols unfeasible on other systems, and the ability to perform imaging of the body as well as the brain. An additional Siemens system, will provide other benefits as well including flexibility of scheduling and easy portability of pulse sequences across magnets, familiarity with the programming and user interface, and compatibility with our ongoing instrumentation development efforts. This badly needed shared instrument will enhance the imaging activities of the many PHS supported research programs at the Martinos Center. [unreadable] [unreadable]